don't print quota lines with missing data

src/mpsd_hpc_tools/quota.py

@@ -95,6 +95,8 @@ def df_mountpoint(path: pathlib.Path) -> Tuple[int, int, int]:
 
 def print_quota_line(location, size, used, avail, rel=None, raw=False):
     format_string = "{:20} {:>14} {:>14} {:>14.4}%\n"
+    if size is None:
+        return
     if rel is None:
         rel = 100.0 * used / size
     if not raw: